Fast switching between the ground- and excited-state lasing in a quantum-dot microdisk triggered by sub-ps pulses

A quantum-dot microdisk was optically pumped by continuous-wave excitation with a level sufficient for the ground-state lasing. The microdisk was additionally illuminated with sub-ps pulses of various powers. It was found that there is a critical level of pulse power that determines the subsequent transient process of the microlaser. Depending on the level of the pulsed excitation, the ground-state lasing intensity can be either enhanced (for weak pulses) or fully quenched (for strong pulses). In the latter case, the excited-state lasing is ignited for a short time. All dynamic phenomena occur on a time scale of the order of 100 ps, and the duration of the transient process as a whole (from the arrival of the excitation pulse to the restoration of steady-state intensities) lasts no more than 0.5 ns. Using this phenomenon, a microlaser can be rapidly switched between two states with the switching controlled by the level of the incoming optical pulse.